558 peculiar stars discovered at Abastumani

Kharadze, E. K.; Chargeishvili, K. B.

doi:10.1086/115336

Cited by 5 publications

(6 citation statements)

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“…We could not apply this method to stars for which neither a parallax nor a U magnitude were available. These objects were detected by Kharadze & Chargeishvili (1990), the only available reference for most of them.…”

Section: Discussionmentioning

confidence: 99%

“…The blue dashed line shows the HI-1A filter throughput, convolved with the CCD quantum efficiency, for which the scale is given by the y-axis on the right hand side of the plot. Kharadze & Chargeishvili (1990). Right ascension and declination are given in degrees.…”

Section: Characteristics Of Stereo Datamentioning

confidence: 99%

“…The blue asterisks show the position in the sky of the 337 mCP stars presented in this work. The clump of stars at RA∼90 deg corresponds to the CP stars identified byKharadze & Chargeishvili (1990). Right ascension and declination are given in degrees.…”

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confidence: 99%

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A photometric study of chemically peculiar stars with the STEREO satellites - I. Magnetic chemically peculiar stars★

Wraight¹,

Fossati²,

Netopil³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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About 10 per cent of upper main‐sequence stars are characterized by the presence of chemical peculiarities, often found together with a structured magnetic field. The atmospheres of most of those chemically peculiar stars present surface spots, leading to photometric variability caused by rotational modulation. The study of the light curves of those stars therefore permits a precise measurement of their rotational period, which is important to study stellar evolution and to plan further detailed observations. We analysed the light curves of 1028 chemically peculiar stars obtained with the STEREO spacecraft. We present here the results obtained for the 337 magnetic chemically peculiar stars in our sample. Thanks to the cadence and stability of the photometry, STEREO data are perfectly suitable to study variability signals with a periodicity typical of magnetic chemically peculiar stars. Using a matched filter algorithm and then two different period searching algorithms, we compiled a list of 82 magnetic chemically peculiar stars for which we measured a reliable rotational period; for 48 of them, this is the first measurement of their rotational period. The remaining 255 stars are likely to be constant, although we cannot exclude the presence of long‐period variability. In some cases, the presence of blending or systematic effects prevented us from detecting any reliable variability and in those cases we classified the star as constant. For each star we classified as variable, we determined temperature, luminosity, mass and fractional age, but the limited statistics, biased towards the shorter periods, prevented us from finding any evolutionary trend of the rotational period. For a few stars, the comparison between their projected rotational velocity and equatorial velocity let us believe that their real rotational period might be longer than that found here and previously obtained. For the 82 stars identified as variable, we give all necessary information needed to plan further phase‐dependent observations.

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Section: Discussionmentioning

confidence: 99%

Section: Characteristics Of Stereo Datamentioning

confidence: 99%

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A photometric study of chemically peculiar stars with the STEREO satellites - I. Magnetic chemically peculiar stars★

Wraight¹,

Fossati²,

Netopil³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…For 51 of these 83 stars, the only source that we could identify for the Ap classification reported by Renson & Manfroid (2009) is the catalogue of spectral classifications of stars in an area of 140 square degrees in the Galactic anticentre direction that was compiled by the Abastumani Astrophysical Observatory (Chargeishvili 1988). The 208 Ap stars discovered as part of the study performed to build this catalogue were listed by Kharadze & Chargeishvili (1990).…”

Section: Classification Issuesmentioning

confidence: 99%

“…This is all the more probable since all of those stars for which an MK spectral type was available in SIMBAD (mostly from the Michigan Spectral Survey) were classified as normal A stars. Thus, while some of the stars from the list of Kharadze & Chargeishvili (1990) must almost certainly be genuine Ap stars, none of them can be regarded as a bona fide Ap star unless there exists some other convincing evidence of its peculiarity. Such evidence was only found for two of the 51 Abastumani stars that we identified as candidate ssrAp stars through the above-described automatic analysis of the TESS data.…”

Section: Classification Issuesmentioning

confidence: 99%

Long-period Ap stars discovered with TESS data: Cycles 3 and 4

Mathys,

Holdsworth,

Kurtz

2024

A&A

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One of the most challenging aspects of the Ap stars is the extreme differentiation of their rotation periods, which span more than five orders of magnitude. The physical origin of this differentiation remains poorly understood. The consideration of the most slowly rotating Ap stars represents a promising approach to gain insight into the processes responsible for the rotational braking to which the Ap stars are subject. However, historically, the study of these stars focused primarily on the most strongly magnetic among them. This bias introduced an ambiguity in the conclusions that could be drawn, as it did not allow the distinction between the rotational and magnetic effects, nor the investigation of possible correlations between rotational and magnetic properties. We previously showed that the identification of super-slowly rotating Ap (ssrAp) star candidates (defined as Ap stars that have rotation periods $ through systematic exploitation of the available TESS photometric observations of Ap stars is an effective approach to build a sample devoid of magnetic bias. This approach rests on the presence of brightness spots on the surface of Ap stars that are not distributed symmetrically about their rotation axes and show long-term stability, hence are responsible for photometric variations with the stellar rotation period. In our previous analyses of TESS Cycle 1 and Cycle 2 data, we interpreted the Ap stars showing no such variability over the 27-d duration of a TESS sector as being ssrAp star candidates. Here, we applied the same approach to TESS Cycle 3 and Cycle 4 observations of Ap stars. We show, however, that two issues that had not been fully appreciated until now may lead to spurious identification of ssrAp star candidates. On the one hand, a considerable fraction of the Ap stars in the existing lists turn out to have erroneous or dubious spectral classifications. On the other hand, the TESS data processing may remove part of the variability signal, especially for stars with moderately long periods ($20\ d After critical evaluation of these effects, we report the identification of 25 new ssrAp star candidates and of eight stars with moderately long periods. Combining this list with the lists of ssrAp stars from Cycles 1 and 2 and with the list of ssrAp stars that were previously known but whose lack of variability was not detected in our study, we confirmed at a higher significance level the conclusions drawn in our earlier work. These include the lower rate of occurrence of super-slow rotation among weakly magnetic Ap stars than among strongly magnetic ones, the probable existence of a gap between sim 2 and sim 3\,kG in the distribution of the magnetic field strengths of the ssrAp stars, and the much higher rate of occurrence of rapid oscillations in ssrAp stars than in the whole population of Ap stars. The next step to gain further understanding of the ssrAp stars will be to obtain high-resolution spectra of those for which such observations have not been made yet, to constrain their rotation velocities and their magnetic fields.

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